Since the 1980's, microcatheter technology has advanced to become commonplace in the treatment of vascular lesions of the central nervous system and other systems having tiny, tortuous vasculature. Microcatheters have been used to treat cerebral aneurysms, fistulas, and arterial venous malformations, for example, by occluding the parent vessel. Microcatheters have been used as well to deliver agents to open occluded vasculature, including agents to dissolve clots. Balloon microcatheters have been used to open vessels narrowed due to atherosclerosis.
Microcatheters have also been used to treat pathological vascular abnormalities through an endovascular approach, using selective deposition of coils, particles, or liquid adhesives. Microcatheters have additionally been used to deliver chemotherapeutic agents to spinal, head and neck, or intracranial malignancies.
Conventionally, for some embodiments, microcatheters have advanced from a femoral puncture through the lumen of a guiding catheter which has terminated in a carotid or vertebral artery. The microcatheter is advanced beyond the guiding catheter using one of two known techniques. One prior art technique has been directing a guide wire through the lumen of the microcatheter which has had varying degrees of tip-shape, torqueability, stiffness and external coating. A second prior art method has included a flow-directed technique in which the microcatheter has been extremely flexible and has been carried by blood flow to the lesion, assisted by of injections of saline or contrast media through the flow directed microcatheter.
Each of the conventional methodologies for delivering a microcatheter has had drawbacks. The guidewire directed microcatheter has involved the risk of puncturing a vessel or aneurysm, which has had the potential of having devastating hemorrhagic consequences intracranially. With the flow-directed microcatheter, it has frequently been difficult to make precise turns and select individual vessels when complex vascular anatomy has been encountered.
A guidewire has not been usable in the flow-directed microcatheter because of the suppleness of the microcatheter and the significant possibilities of puncturing the wall of the microcatheter with a stiff guidewire. This risk has also prohibited the delivery of coils which have been used to assist in occlusion, through a flow-directed microcatheter. Thus, only liquid adhesive or tiny particles have been injected through the flow-directed variety of microcatheter for vascular occlusion, the tiny particles usually of insufficient size to achieve the desired vascular occlusion. Conversely, the guide-wire directed microcatheter often times has not been pushable from the groin over a guidewire through multiple turns in branching intracranial vascularity to reach the desired vessel.
In one prior art attempt at improvement of these techniques, a method has been developed to incorporate a balloon into the tip of a microcatheter to allow the blood flow to carry the distended balloon distally to the desired target vessel. The disadvantage with the balloon technology is that two lumens have been required, one for the lumen to deliver the embolic agent, and the second balloon to inflate and deflate the balloon. Alternatively, a calibrated leak balloon has been incorporated in the tip of the microcatheter. This, however, has not allowed for directionality and has not been usable with a guidewire.